Boulder Police are investigating after at least six men overdosed on potentially tainted drugs at the Kappa Sigma fraternity Saturday night. Police said officers responded between 10 p.m. and 10:30 p.m. to the hospital and to the fraternity house at 1100 Pennsylvania Avenue. Police spokesperson Dionne Waugh said when officers arrived, they found people visibly sick and throwing up. Waugh said naloxone was administered. According to the University of Colorado Boulder, the six young men taken to the hospital were students partying off campus at the expelled fraternity house. Following the incident, Boulder Police said one man's condition was considered grave but has since improved. All the students involved are expected to survive. Police believe the men had ingested a possibly tainted batch of cocaine. Alcohol was also involved at the party. While it's not known what could have been mixed with the cocaine – one possibility is fentanyl. Read the full story: https://www.9news.com/article/news/local/boulder-cocaine-overdose-tainted-drugs/73-b74f89f8-ef70-4005-990a-367cda5bbda9 More local videos here: https://youtube.com/@9news Subscribe to NEXT: https://youtube.com/@Nexton9NEWS Stay connected: 9NEWS Website: https://www.9news.com/ Facebook: https://www.facebook.com/ilike9news Twitter: https://twitter.com/9NEWS Instagram: https://www.instagram.com/9newsdenver/ Download the 9NEWS App: https://www.9news.com/appredirect/ Sign up for the 9NEWSLETTER: https://www.9news.com/email 9NEWS (KUSA) is located in Denver, Colorado.